1. Field of the Invention
The present invention relates to athletic training devices and methods and, more particularly, to training devices and methods for fostering the proper timing of the swing of an athletic implement such as a golf club.
2. Description of the Prior Art
In athletic games wherein a bat, club or racket is used to strike a playing object, such as a ball, it is well recognized that successful play is largely dependent upon the proper swing or stroke employed. This is overwhelmingly the case with golf, and much has been written descriptive of what a perfect golf swing should comprise.
The swinging of a golf club entails the transfer of energy from a golfer's muscles to the angular momentum of the body, arms and golf club, and finally to the kinetic energy of the club head as it impacts the golf ball. The golfer's legs, hips, torso, arms and wrists all participate in these motions, progressively transferring energy from the muscles of the body to the kinetic energy of the moving club head. As the club is accelerated during approximately the first two thirds of the downswing, the club shaft is bent rearwardly away from the ball. During the last third of the downswing, the angular momentum of the system is transferred to club momentum by the golfer in uncocking his wrists. This rotation within an already rotating system gives rise to a Coriolis acceleration which, in addition to the other continuing energy inputs into the system during the swing, causes the club shaft to unbend and whip the club head forward into the ball.
It is obvious that there is a maximum transfer of potential energy from the bent club shaft to the moving club head at the instant that the club shaft straightens. If the shaft is still appreciably bent to the rear at impact, some unused energy remains in the bent shaft, and the momentum of the club head is less than a maximum. On the other hand, if the shaft straightens before impact, some of the kinetic energy of the club head is wasted by being converted into potential energy in bending the club shaft forwardly. In this instance, the momentum of the club head is reduced below an attainable maximum before impact. The bending of the shaft is a fine-grained, vernier type of motion included within the rotation of the club about the wrists and the rotation of a club and arms about the golfer's body. As such, shaft bending or flexing provides accurate insight into the mechanics of the motion. Hence, a sensor on the club shaft is a valid and perceptive indicator of the correctness of the timing and force of the swing.
Many prior art devices have utilized the information yielded by a sensor mounted on a golf club shaft in a variety of ways. Many of these, such as those disclosed by Evans in U.S. Pat. Nos. 3,270,564, 3,717,857, 3,788,647, 3,792,863 and 3,806,131 and Hammond in U.S. Pat. No. 3,945,646 are devices which sense flexural movement of the club shaft by means of a strain gauge, and display this and other measured parameters on a cathode ray tube as a function of time. While the information derived is valuable, at least a brief period of time is required to analyze it in order to determine the effectiveness of the just completed swing. Other devices, such as those of Kirkman, U.S. Pat. No. 3,106,403 and Moore, U.S. Pat. No. 3,677,553 are more simplistic in their approach and provide more immediate feedback. In these devices, an indicator light mounted on the shaft or head of the club is illuminated when the proper amount of centrifugal force is achieved during the swing.